Studies of the influence of lipid-protein interactions on the activity of UDP-glucuronyltransferase will be continued. We will try to remove all residual phospholipids from inactive, but activatable, preparations of the enzyme. Activation of the inactive "apo-enzyme" preparation then will be studied as a function of the properties of selected pure lipids, and mixtures of lipids. Complete kinetic analyses will be carried out on activated preparations in order to determine whether variations of the type of lipid added back produce different forms of UDP-glucuronyltransferase.